EMG and NCV Testing Flashcards
Do you need board certification?
No, only for Medicare reimbursement
Signs & symptoms that warrant electrophysiological testing? (8)
- Paresthesias
- Weakness
- Muscle pain that doesn’t fit pattern of ache/strain
- Neurogenic pain
- h/o trauma or repetitive stress
- Delayed recovery of orthopedic injury (ankle sprain grade 2 & 3) >> Neurogenic inflammation
- Unexpected weakness post surgery
>> Anterior THR Tourniquet, traction
>> Radial artery graft Isolated blood supply to median/ulnar nerves
• Patients with mid-cervical SCI
>> Determine distal nerve integrity prior to undergoing tendon transfers
Electrophysiological testing purposes? (6)
- Identify presence of nerve injury or muscle disease
- Identify which nerve(s) or muscle(s) are damaged
- Characterize injury
>> Fiber types, severity
• Identify where damage is
>> Focus treatment plan
• Determine stage of tissue healing
>> Does not always match time of injury
• Determine prognosis
>> Estimate recovery time
Electrophysiological testing precautions/contraindications? (6)
- Bleeding risk: Pts. on coagulotherapy, platelets < 50,000/mm3
- Infection risk: Lymphedema, immune compromise (HIV or other)
- Specific sites: Pneumothorax, peritoneal insertion, biopsy site
- Avoid stimulation on pts with implanted electrical devices,
- pregnant pts - PATIENT DISCOMFORT!!!!!
Nerve conduction studies (NCS) measure? How?
- Measure how well a peripheral nerve can conduct an induced stimulus = evoked potential
- Electrically stimulate/activate nerve at various points along the superficial path of the nerve & record output at target organ
NCS areas for testing and their corresponding study type? (3)
- Muscle = motor nerve conduction study
- Skin = sensory nerve conduction study
- Proximal nerve components = late responses (H-reflex & f-wave)
NCS measurable characteristics - what is distal latency? Useful for?
• Distal latency – time it takes for electrical signal to reach target tissue from the most distal point of stimulation
- Useful for distal entrapment neuropathies (carpal/tarsal tunnel syndrome)
NCS measurable characteristics - what is conduction velocity? Useful for?
• Conduction velocity – time it takes for electrical impulse to travel between two given points along course of nerve
- Useful for proximal entrapment neuropathies (cubital tunnel syndrome)
NCS measurable characteristics - what is amplitude? Useful for?
• Amplitude – measure of how many working axons are activated when nerve is electrically stimulated
- Useful for systemic conditions (diabetes)
NCS tells us? Helps to?
• Tell us specifically what component of the nerve is injured
- Helps determine prognosis & guide treatment
Latency & velocity are measures of? Speed of a nerve is determined by? What indicates a myelin problem? Slowing identifies what?
- time
- myelin integrity
- Prolonged latency or slow velocity indicates myelin problem
- Slowing identifies where the compression injury is
Amplitude is measure of? Output of nerve is determined by? Low amplitude indicates?
- signal strength
- axonal integrity
- axon problem (most of the time)
Onset/Peak Distal latency = ? Amplitude = ? Velocity = ?
- how fast nerve travels in distal segment
- how many axons are firing when nerve stimulated
- how fast nerve travels btwn limb segments
F/H Latency = ? L-R F/H latency = ?
- how fast nerve travels in entire segment
- how fast nerve travels compared to opposite limb
NCS good for detection of? (4)
- Compression neuropathies (CTS)
- Plexopathies
- Demyelinating polyneuropathies (GBS)
- Neuromuscular junction disorders (Mysethenia Gravis)
NCS poor for detection of? (3)
- Radiculopathies (except H-reflex for S1)
- Myopathies (muscular dystrophy)
- Lower motor neuron disorders (ALS)
EMG determines? It is? Needle acts as? Detecting? Displaying? Examines what? (3)
- Determines the integrity of all components of a motor unit: alpha motor neuron, axon, all muscle fibers innervated by that motor neuron
- Invasive: needled recording electrode inserted through skin and fascia into various depths of the muscle
- Needle acts as antenna, detecting electrical impulses of motor units & displaying as waveforms
- Examines 3 states of the muscle: at rest, with minimal voluntary contraction, increasing effort of voluntary contraction
EMG Resting assessment steps? (3)
- Insert needle into muscle
- Move needle into different depths & quadrants
- Observe electrical activity generated
Normal Resting Assessment - what kind of insertional activity? (2)
- Brief discharge of electrical activity cause by mechanical stimulus of muscle fiber
- Electrical silence after needle stops moving
Abnormal Resting Assessment - decreased insertional activity indicates? Increased?
- Indicates muscle fiber fibrosis/necrosis
- Precursor to spontaneous potentials
Another abnormal resting response? How do they appear?
- Spontaneous potentials
- Sustained waveforms that appear @ rest
Types of spontaneous potentials? (5)
- Fibrilation potentials (Fibs)
- Positive sharp waves (PSW)
- Fasiculation potentials
- Complex repetitive discharges (CRD)
- Myotonic discharges
Fibs and PSW caused by?
Caused by muscle fiber denervation – electrical discharge of muscle fiber w/o input from nerve
Fasiculation Potentials are? Often accompanied by? Only considered abnormal if?
- Spontaneous irregular discharge of motor unit w/o voluntary control
- Often accompanied by visible or palpable muscle twitch
- consistently present and in diffuse muscles of the limbs and/or face
